


The Baby-Sitter Experiment

by nightwalker



Category: Avengers (Comics), Marvel Adventures: Avengers
Genre: Domestic Avengers, Domestic Fluff, Established Relationship, Fluff, Kid Fic, Luke/Jess/Danny in the background, M/M, Relationship Discussions
Language: English
Status: Completed
Published: 2014-10-27
Updated: 2014-10-27
Packaged: 2018-02-22 19:55:02
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 4,681
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/2519828
Author URL: https://archiveofourown.org/users/nightwalker/pseuds/nightwalker
Summary: <blockquote class="userstuff">
              <p>Steve and Tony volunteer to babysit. Fluff ensues.</p>
            </blockquote>





	The Baby-Sitter Experiment

**Author's Note:**

> Thanks to humantrampoline85, because I couldn’t come up with anything to write so she just spammed me with one awesome prompt after another. And thanks to musicalluna for giving this a once-over for me so I could post it without embarrassing myself. And thanks to everyone who pitched in and helped me with the lab equipment. My dash is full of awesome science people. Thank you!

Luke held his daughter against his chest like he was afraid what would happen if he let her go. “You’re sure about this?”

Steve shot a glance at Tony, but to his credit, Tony didn’t look insulted, only amused. “Luke. What do you think I’m going to do to her?”

Luke hesitated for a minute and that was long enough for his wife to sweep in and lift Danielle from his arms. “Worst case scenario,” Jess said as she plopped the baby down into Tony’s waiting arms, “he turns her into a cyborg. But at least she’d be a very well-built cyborg.”

“That’s not funny,” Luke objected. He crossed his arms over his chest and very clearly resisted the urge to take his daughter back.

“It’s hilarious,” Tony said. He settled Danielle against his shoulder with an ease that Steve wouldn't have expected and kissed her forehead. “Dani doesn’t want to be a cyborg, do you, sweetheart?”

Dani buried her face against his shoulder.

“See?” Tony asked. “I’d never make Dani be a cyborg if she didn’t want.”

“There you go.” Jess thrust a suitcase nearly as big as she was at her husband, forcing him to grab for it. “Disaster averted.”

“Look, we don’t leave her with babysitters very often,” Luke said. “Well, I mean-“

“Danny and your mom are family,” Tony said. “I get it. It’s different when you’re leaving her with someone else. But we’ve got a dozen other people here to back us up and we’ll check in with you two everyday. We’re going to be fine.” He rocked Dani side to side for a minute. “Right, squirt? You going to hang out with Uncle Tony and Uncle Steve this week?”

She peeked out at him shyly. “Hi, Uncle Tony.”

Jess caught Danielle’s face between her hands. “Mommy is going to miss you so much!” She pressed a kiss against the little girl’s cheek. “You behave, okay? Uncle Steve is old and Uncle Tony has a heart condition, so you take it easy on them.”

Dani nodded and hid her face against Tony’s chest again while he glared at her mother. Jess just grinned at him. “Thanks again, Tony. We appreciate you and Cap helping us out.” She gave Luke a pointed look and he nodded reluctantly. “If you hadn’t volunteered, we would have had to reschedule our first vacation since before Danielle was born. And if that had happened, I probably would have done something crazy, like file for divorce.”

Luke rolled his eyes. “Thank you.”

Tony hit a grin against Danielle’s hair. “It’s really no problem. Babysitters cancel. It happens.”

“Just don't go installing anything on her,” Luke said. “And don't buy her anything. I mean it, Stark, she's two years old, she doesn't need a car. We understand each other?”

“No cars,” Tony said solemnly, with a half-grin on his face that Steve knew from long experience meant he would be going out of his way to buy her everything _but_ a car just to get on Luke's nerves. Steve surreptitiously elbowed Tony in the ribs, but ended up jostling Dani, who squirmed in Tony's grip and made a high-pitched whine. Steve winced, expecting tears, but Tony just hummed and rocked her in his arms a little.

“Okay, time to go, before someone starts fussing.” Jess grabbed a battered green duffel bag and slung it over her shoulder. She dropped a kiss on Dani's head. “Be good, baby. Mommy will be back soon.”

Luke hesitated as she started for the door. “We're going to miss our flight,” Jess said.

“It's a private jet,” Luke said. He cupped the back of Danielle's head and brushed a kiss over her curls. “It's not like Danny's going to leave without us.”

“He will if I get there first!” Jess blew a kiss at Dani, who was watching her parents with wide, slightly watery eyes. “Move that butt, Mr. Cage, or Danny and I will be going on our honeymoon without you.”

“I think she'll do it,” Steve said. He couldn't help but smile as Luke lingered. Tony held Danielle out for Luke to hold her one last time, but he shook his head. Tony resettled her against his chest where she began to whimper. 

“She would. Danny wouldn't.” Luke flashed them both a quick smile. “At least not for a few more minutes. Stark. Do not mechanize my firstborn. Rogers. When he inevitably tries to mechanize my baby, do not let him.”

“Deal,” Steve said over Tony's sputtered indignation. “You three have a great trip. You deserve it.” He waved goodbye as Luke hefted the last of the luggage and descended the front steps toward the car that was waiting for them. Jess waved back from the backseat, and then they were gone.

“So,” Steve said, trying to sound more confident about the next two weeks than he really was. “What should we do- “ He turned to his side, but his husband and the baby were both gone. “Tony?” 

****

“No, that's a freezer, not a refrigerator. No snacks in the lab. Don't get any closer, that's where we keep the liquid nitrogen.” Tony's voice drifted up from his workshop. “Do you know what liquid means?”

Steve paused in the entryway of the workshop. The glass doors were wide open and Tony was pacing Danielle as she slowly explored the space. She was walking with her hands behind her back but every now and then she'd stop and point at something. “That's the hard drive from Uncle Peter's computer. Always update your malware protection, kiddo. Words to live by.”

Dani nodded solemnly, as if the words struck a chord within her, then pointed to a tangle of cords handing out of the bottom drawer of a filing cabinet. 

“Those are Christmas lights,” Tony said. “Sometimes Uncle Steve likes to hang up Christmas lights and surprise me with a romantic dinner. That's nice of him, isn't it?”

Danielle crouched down to reach for something under Tony's workbench. “I'm just letting you know, that anything down there is probably trash. What's the rule when we're in Uncle Tony's workshop?”

Danielle quickly clasped her hands behind her back again.

“Good girl.” Tony held out his arms and she skipped over to him. He swung her up and sat her down on the edge of his worktable. “Okay. You can touch anything that's on the table, deal?”

There were a few tools laid out carefully on the table, plus some papers and a framed photograph. Steve drifted closer and recognized the blueprints for an old version of the Iron Man armor. 

Danielle picked up the picture first, holding the frame tightly in her little fists. She examined it curiously, then held it out for Tony. “Mommy?”

“Yeah. That's when your mom first joined the Avengers. We threw a big party for her. See?” Tony pointed to the picture. “Look how happy your dad looks. And if you look in the back you can see Uncle Logan wearing a cowboy hat.” He leaned in close and lowered his voice to a whisper. “We never really figured out why.”

Danielle giggled at him and handed him the photo so he could reset it carefully on the table. She rolled up onto her knees and carefully inched her way across the table so she could examine the other items.

Steve leaned against the auto-assembler and watched them. He'd have assumed, years ago when they first started expanding the team that had so rapidly become their family, that Tony Stark was as bad with kids as Steve himself. But he'd been proven wrong quickly, and over the years Tony's skill with kids had become just another of the things Steve loved about him. Steve couldn't talk to anyone under eighteen without feeling like a 90-year-old clown and smaller children made him so nervous that he could barely bring himself to hold them – babies were squirmy and messy. There was a part of him that still remembered being sickly and small and heard his mother's regretful warnings in the back of his mind, that playing with the other children would only make him sicker. That he'd have to wait till he was stronger and whatever childhood illness that was circling had gone away. Neither of those things ever really happened and aside from Bucky and sometimes his sisters, Steve never really socialized with kids outside of school. 

But Tony, Tony was a natural. He talked to them like they were people, never condescending or using incomprehensible baby-talk. He was comforting and gentle without being coddling. He _liked_ kids, and it showed every time he was around them. Steve thought Tony would make an amazing father. Sometimes Steve thought about that a lot.

Over on the workbench, Tony was showing Dani how to use his handheld to bring up the bright blue-white holographic schematics of the Tower. “That's your room,” he said, and the space lit up bright yellow. “Here.” He handed her the handheld, making sure she had a firm grip on both sides before he let go. “Can you show me where we are now?”

The sublevels lit up bright yellow and Danielle beamed up at him when he congratulated her.

“What are you two getting up to?” Steve asked.

Tony gave him an easy smile. “I thought Dani would like a tour of the workshop.”

“I'm not allowed in the workshop,” Dani said. Her words were soft around the edges and Steve sometimes had to take a second to figure out what she was saying, but Tony was nodding in agreement. “But Uncle Tony said no touching.”

“That's right. Dani promised not to touch _anything_ without my permission, so I thought it would be okay. It's a special occasion, after all. Her first big-girl sleepover without Mom and Dad.” he ruffled her hair. “Dani's a natural down here, Steve. I think she could be an engineer when she grows up.”

“No,” Dani said, pursing her lips and drawing the word out. “No, I wanna be a ninja.”

“Your Uncle Danny would not approve,” Tony told her. “But when you're ready, let me know and I'll make you the coolest ninja outfit you ever saw.” 

“Why am I suddenly picturing a child-sized Iron Man armor done all in black?” Steve asked.

Tony gave him an innocent look. “I have no idea what you're talking about. But it would be awesome, wouldn't it?”

“Luke would kill you,” Steve said.

“He wouldn't.” Tony looked at Dani. “Your daddy loves me lots, doesn't he?” 

Dani shook her head solemnly and Tony burst out laughing. “Lies! Hey, Dani, wanna see how I paint my Iron Man armor? If you want, you can hold the paint sprayer.”

****

Five hours later Steve was showered, changed and standing outside the brightly lit entrance of FAO Schwarz with Dani's little hand clasped firmly in his own. “Didn't Luke say not to buy her anything?” He studied his fingernails, but he was fairly certain he'd gotten the last of the bright pink paint off.

“Luke said not to buy her a car, Steven.” Tony had a thick smear of pink paint on the back of his neck that he'd somehow missed. Steve, who had expressed concerns about letting a not-yet-three-years-old girl handle a paint sprayer and been soundly ignored, chose not to point it out. “We're just going to get Dani her own little toolbox.” 

Inside the store was a whirl of colors and sounds and Steve immediately lost track of his husband and Dani. He briefly considered tracking them down and putting a stop to whatever grandiose shopping spree Tony undoubtedly had planned, but instead he decided that what he didn't know about, he wouldn't have to explain to Dani's parents later on. He ambled around the store, dodging excited kids and waving off helpful store employees. The store was... massive. He'd never been inside before, and there hadn't been anything like it when he'd been younger. The displays were elaborate; a shelf shaped like a pineapple that held stuffed animals, a giant dinosaur display, a teddy bear the side of Thanos himself, surrounded by massive building blocks. There were life-sized dolls dressed up in child-sized Halloween costumes, and a Barbie Foosball table that Steve found slightly creepy. Models of spacecraft hung from the ceiling and one wall was lined with huge plastic tubes of brightly colored candies. 

Steve filled a bag with a dozen or so different types of candy, then picked out a doll he thought Danielle would like, a baby girl doll with light brown skin and tightly curled brown hair almost the exact same shade as Dani's. He then managed to get lost in a roomful of Legos and ended up buying a half dozen different Avengers-themed sets because they had Power Man and Iron Fist in them. 

He also bought a plush Iron Man doll because he could.

He was wandering through aisles of kid's art supplies – crayons and washable markers, rows and rows of coloring books – and trying to decide if Danielle would like any of them, when someone small and very strong flung themselves at top speed against the back of his legs.

He jumped a little, then caught himself. “There you are! I thought you got lost!”

Danielle, who was now wearing a ninja outfit with a bright blue ballerina tutu, Captain America sneakers that lit up whenever she moved and carrying a fairy princess wand in one hand and a plastic battle-axe almost as big as she was in the other, beamed up at him. “Uncle Tony says we can go to the face painting lady,” she said. She held out her magic wand and Steve accepted it solemnly. Then she wrapped her hand around two of his fingers and tugged. Steve looked up and Tony was watching them both with a warm smile, his eyes a bright electric blue that took Steve's breath away for a minute.

“We're going to get our faces painted,” Tony said, and Steve leaned over to kiss his cheek. “Dani wants to get a kitty face.”

“No, now I want to be Batman,” Dani said. “Or a dinosaur.”

She ended up with a half-mask of Spider-Man on one side and a rainbow-colored butterfly wing on the other side. Copious amounts of glitter were involved, and she was trailing sparkles as she danced around the chair while Steve sat patiently letting the face painter draw fluffy white wings around his temples, with the Cap logo between his eyes. Tony, who had flat-out refused to have his entire face painted like the Iron Man mask, had negotiated his way down to a blue eyemask with the Superman logo between his eyes and was watching Steve with a grin and no small amount of amusement.

“The paparazzi are going to love this,” Steve said and the face painter scolded him for moving.

“They've seen worse,” Tony said with a one-armed shrug. “I think you look good.”

“Can I have a bike?” Dani asked.

“Too much like a car,” Tony told her. “Your dad said no cars.”

Danielle nodded as if that made perfect sense, then bit her lip while she thought. “Can I have a _horse_?” she asked. 

“Oh yeah,” Tony said. “That's the total opposite of a car.”

“ _Tony_ ,” Steve said, but the face painter shushed him again and Tony took Danielle's hand and disappeared in a trail of glitter.

Steve sighed. Well, she was going to end up spoiled and hyper but at least she wasn't a cyborg.

It was a couple minutes before the painter released him and Steve gathered their assorted purchases. He found them in front of a display of stuffed animals, gravely examining three different plush horses. One was small enough for Dani to carry in her pocket, one was the size of a teddy bear, and the third one was big enough that Tony could have sat on its back easily. “How would we get it home?” Steve pointed out. 

Tony gave him a strange look. “In a car?”

“Luke will kill you,” Steve said. “That thing's almost as big as he is.”

Danielle, fortunately, settled for the smallest one, but then she and Tony had to pick out a purse for her to carry it in. The bright purple purse was shaped like a flower and Dani arranged it so that her horse's head could peek out of the top.

“I'm hungry,” she announced. “Can I have candy?”

“No,” Tony said, and Steve, who had started to reach for the bag he'd picked out earlier, hastily stuffed it back in his shopping bag. “If you're hungry then we should get dinner. Candy is for dessert, right?”

“Right. Can I have some for later?”

“That sounds fair. Come on.” Tony held out his hand and she curled her little fingers around his. “Let's go get all your toys wrapped up and then maybe Uncle Steve will take us out to dinner. What do you want? Pizza?”

“Can I have a hot dog?”

Tony pretended to think about it as they made their way to the cashier. “Only if you have a vegetable with it.”

****

Steve was put in charge of preparing dinner since Tony claimed that he and Danielle had top secret work to do in the TV room. Steve was tempted to peek while he cooked; he could hear Dani's high-pitched giggles and occasional shriek of laughter, as well as lots of thumps and the sound of furniture being rearranged. 

On the way home, Dani negotiated them down to an apple and milk instead of vegetables, which Tony declared to be satisfactorily healthy. So Steve cut a few hot dogs into bit-sized slices and let them fry in a pan while he sliced apples and poured three glasses of milk. “I'm coming in!” he called, arranging their dinner on a tray.

“Uncle Steve help!” Dani burst out into giggles. “Help!”

Steve swept through the door into the TV room as dramatically as he could without dropping everything. “What's going on in here?” he asked in his best super-hero voice (not the Cap voice, which he had been informed could scare small children when he used it suddenly, but a fake deep voice not unlike the Batman cartoons that Clint and Tigra liked to watch). He set the tray down on the coffee table and surveyed the fort Tony and Dani had built out of what appeared to be all the couch cushions and a set of hideously floral sheets Steve had never seen before. It took up all the space in front of the television and when Dani lifted the flap to peek out at him, he saw a pile of what must have been half the pillows in the mansion. “Are you being held prisoner in there?' he asked her.

“No,” she said, clutching her little stuffed horse to her chest. “I'm hiding from Uncle Tony. He tickles.”

“He does tickle,” Steve said. “But if you want to come out and eat your hot dog, I promise to protect you.”

Dani power-crawled her way out of the fort and plopped herself down in front of the coffee table.

“Traitor,” Tony said. He crawled out of the fort as well, his hair mussed up and his eyes sparkling. He'd wiped off his face paint at some point, but the smear of pink was still there. “Ooh, milk. Can I have chocolate in mine?”

“If you have chocolate milk, you can't have dessert,” Steve said, noting the way Dani's eyes lit up.

“Fair enough.” Tony sat down across from Dani and tugged on the leg of Steve's jeans. “Come on, grab a seat.” He leaned into Steve's side for a moment and pressed a kiss to the side of his throat. “Dinner looks great.”

It looked like fried hot dogs and apple slices, but any meal that didn't come out of a cold can behind enemy lines was a good meal, in Steve's book. He slid an arm around Tony's waist while his husband poured a little ketchup and mustard onto Dani's plate and let her dip her hot dog pieces into it. “When you're older, I'll tell you how to make the special sauce.”

Dani ended up with ketchup and mustard all over her face and hands, but Steve ran back to the kitchen for paper towels, so her new ninja suit and tutu were spared. Tony whisked her off for a bath after dinner while Steve cleaned up the kitchen. They weren't back by the time he was done, so he dug out the bag of candy he'd gotten for Dani, and then ran down to Tony's lab to pull out the Christmas lights he kept stashed down there.

The pillow fort was remarkably stable – not surprising considering who'd built it – and it wasn't hard to drape the lights all around it. He plugged them in and then turned off the room lights as he waited for them to return.

Dani approved, examining the lights from all angles as she ran around the fort in her nightgown. Her curls bounced around her face as she ran up to Steve. “Are we camping?”

It was about as far from camping as they could get, sleeping on feather pillows in a mansion in Manhattan, but why the heck not? It was kind of like a tent. “We sure are. Now go grab your spot before Tony takes the best one.”

“We both know who the real pillow hog is in this room.” Tony slid both arms around Steve's waist and rested his chin on Steve's shoulder. “This is nice, Steve.”

Steve covered both of Tony's hands with his own. “Well, I had to come up with something before Uncle Tony totally outshone me.” 

Tony chuckled, his breath warm on the side of Steve's neck. “Never. You're my star.” He kissed Steve's shoulder. “Come on. Let's get comfy. I told Dani she could pick the movie.”

It turned out that Danielle could work the Netflix queue like a pro, and in no time she had them watching an animated show about talking horses with tattoos. Steve was really only listening with half an ear, curled up against Tony's back on a mound of pillows, listening to Tony and Dani as she tried to educate them on the lives of her favorite horses. 

“That's Dash,” Dani said, “because she's super-fast. Mommy says that dash means fast, so it's like her codename. Dash is a superhero like Mommy and Daddy.”

“What about that one?” Tony asked. “What's his name?”

“Uncle Tony,” she said in the long-suffering tones of a small child who knows her grown-up will never understand. “That's Twilight and she's a girl. They're all girls except Spike.”

“Spike is a pretty manly name,” Tony agreed. “So who's your favorite?”

“Rainbow Dash,” Dani said promptly, which, yeah, Steve had seen that coming. “When I'm older I'm going to marry her and we can race and make lightning.”

“Good plan,” Tony said. “Much more solid than a lot of adult relationships I've had. Can I marry Apple Jack when I grow up?”

Dani's face scrunched up. “Apple Jack is boring.”

“She's hardworking and honest,” Tony said. His hand found Steve in the pillow nest and he interlocked their fingers. “Good old-fashioned American values. I find that attractive in a cartoon horse.”

Steve knew there was something wrong with him that that made him blush.

“Uncle Steve has to get married too,” Dani said.

“Uncle Steve's already married to me,” Tony said, and Steve squeezed his hand with a grin because Tony actually sounded disgruntled about Steve marrying a cartoon.

“Yeah, but if you can marry Apple Jack then it's not fair unless Uncle Steve can get married too.” Dani yawned into her pillow. Her eyes had been drifting slowly shut for most of the episode. “He should marry the princess cause she's the boss like him.”

“Are there any handsome inventors on this show?” Tony asked. “How about philanthropists?”

“No, they're ponies not filth-and-thros,” Dani said with great effort. “Uncle Steve, Uncle Tony's making stuff up again.”

Steve curled a little closer around Tony's back, and let their voices wash over him.

****

When he woke up, the Christmas lights were still on, but the pinkish light of early morning was peeking in around the edges of the fort.

At some point the TV had been turned off and the front of the fort closed off, so the three of them were completely enclosed. It was cozy and warm with Tony wrapped up in his arms and Dani sprawled on her stomach between them.

Steve brushed a finger over the line of Tony's jaw, listening to his husband breathe. Danielle was so small and so warm between them, such a tiny little person and so trusting in her sleep. Steve had to close his eyes against a sudden wave of emotion and when he opened them again, Tony was awake and blinking up at him.

“Morning,” Steve said in a hushed voice and he lowered his head to give his husband a slow, lingering kiss. He thought this might be something close to perfection, this lazy, easy closeness. This might be something like everything he'd ever needed.

Tony hummed into the kiss and when they parted he leaned down to brush a kiss over Dani's forehead. “That went pretty well, I think,” he said. “We did a good job of keeping her distracted. She didn't cry about her parents leaving at all.”

“It was nice,” Steve agreed. “She's a good kid.”

“Yeah.” Tony smiled down at her, then up at Steve. “We should get one of these someday.”

Steve's next breath caught in his throat. “Yeah,” he said thickly, swallowing around the lump that was trying to choke him. “Yeah. _Yes_. We should – you'd be an amazing father. I want to see you holding our child one day.” He kissed Tony again, deeply, smiling against his husband's mouth. “I love you.”

“I love you,” Tony said. 

“You're squishing me!” Danielle announced loudly. “Can I have some more candy?”

“No,” Steve and Tony chorused, drawing back from each other so they could look at her. 

“Okay.” Dani squirmed out from between them, her curls all awry and her pajamas wrinkled. She'd managed to lose a sock at some point in the night. “Then can I have a pony?”

Tony laughed. “Oh, I have taught you well, grasshopper. Your negotiating tactics need some work, though.”

“Luke's gonna kill us both,” Steve said. “We're going to have to get our own kid after this, because he'll never let us babysit again.”

“Overall, not a bad plan,” Tony said. He sat up and tugged Steve after him as Dani scrambled out of the fort. “Come on, let's get some practice in and see if the novelty wears out before her parents come back.”

Steve gripped Tony's hand. “It won't.”

“No.” Tony leaned in for one last quick kiss. “I know it won't. Next week you and I have some planning to do.”

Steve wrapped one hand around the back of Tony's neck. “Tell me you really want this and you're not just saying it because you think I want it. Tell me you're happy about this.”

“Jesus, Steve.” Tony looked him in the eye, and there was a smile tugging at the corners of Tony's mouth, his eyes were bright and warm like the sky on a spring day. “I don't think I've ever been happier.”

“Guess what?” Danielle declared loudly from somewhere in the next room. “Uncle Steve and Uncle Tony are going to have a baby and I'm getting a pony!”

“Can it fly?” Jess Drew asked. “Hold out for a flying pony. Hey, if you two are making babies in there, I don't want to know about it, but there's a very wriggly ninja-princess out here who seems to be under the delusion that Hulk and I know how to make pancakes.”

Tony scrunched up his face. “No. Still happy. Go figure. Come on, Apple Jack, let's go make pancakes.”


End file.
